1. Field of the Invention
The invention relates generally to a method for calibrating and using a non-contact position measuring instrument having a plurality of sensors disposed spatially proximate to a movable position indicator and, more particularly, to assigning of a length value to a signal generator when its output is a predetermined value and storing of the length values for later comparison in determining unknown positions of the position indicator.
2. Description of the Prior Art
A non-contact position indicator is disclosed in German Pat. OS No. 32 44 891 in which a magnet is mounted for movement parallel to a plurality of magnetic sensors. For each position of the magnet, the sensors are individually interrogated over the entire range of influence of the magnet to produce a positional voltage distribution. For each positional dislocation of the magnet, a new positional voltage distribution is produced which is uniquely identifiable with the magnet position.
In a calibration pass, the characteristic positional voltage distributions are assigned to individual magnet positions and stored in memory. In later measuring passes, an unknown position of the magnet is thereafter found by allocation of a measured positional voltage distribution to the stored positional voltage distributions. Thus, by attaching a magnet to a movable part, a position indicator can be provided.
Such a position indicator requires that, for extremely long position indicator paths, a large number of voltage values must be stored. Also, changes in the spacing between the position indicator and the sensors in the signal generator can change the positional voltage distribution under certain conditions, and variations in the magnet can also lead to changes in the voltage distribution resulting in inaccurate position indications, or possibly even unidentifiable magnet positions.